In the prior art, a wide variety of shapes have been used to harness the power of air in sails for vessels. Further, it has been suggested to use airfoils mounted vertically as the sail means.
In my prior art U.S. Pat. No. 4,655,122, I disclosed an improved aerodynamic shape which comprised essentially a planar face portion and leading and trailing edge portions associated with opposite ends of the face portion to form a pan-shaped enclosure. These shapes were used as blades in an air damper; where one or more blades were pivoted for rotation within a frame. In that environment, the blades provided an increased lift when forced to open by air escaping from a structure.
In my work with windmills, I experimented with various shaped blades, such as that disclosed in my U.S. Pat. No. 5,599,172 for a wind energy conversion system; which had an additional lip on the trailing edge.
In my U.S. Pat. No. 5,711,653, I disclosed an airfoil design with a 90.degree. flange depending from the trailing edge. This displayed improved lift characteristics.
Sails, however, develop their own unique problems unrelated to environments where airfoils are normally used; such as, in particular, the fact that the sails flop back and forth from port to starboard and back again, depending on the direction of the wind. Thus, each side of the sail is acted upon in a different manner rather than being constantly impinged upon in a uniform manner.